Interplay between magnetism and chemisorption:: a theoretical study of CO and NO adsorption on a Pd3Mn alloy surface

The chemisorption of CO or NO is compared on the Pd3Mn surface which presents both non-magnetic (Pd) and magnetic (Mn) atoms. Density functional theory calculations show that CO prefers to adsorb atop a low-spin Pd atom and NO atop a high-spin Mn atom. This contrasts with the bare Pd(100) surface where both adsorbates prefer the higher coordination bridge or hollow sites. The magnetic moment of NO, only partly decreased, shows an antiferromagnetic coupling with the Mn magnetic moment. A strong stabilizing interaction is shown between the partially occupied 2 pi NO spin-orbitals and the mainly empty d(xz) or d(yz) Mn spin-orbital. (C) 1999 Elsevier Science B.V. All rights reserved.